G. Speranza

Spontaneous beat-to-beat variability of the ventricular repolarization duration

The spontaneous beat-to-beat variability of the ventricular repolarization duration was investigated in 21 healthy subjects (age 25-71 years; mean, 40 years) during the basal state in a recumbent position. For each subject, approximately 1,000 consecutive cycles were analyzed with an automated technique. The time series of the RR, QT, and RT intervals generate histograms that approximate normal distributions and have mean standard deviations of 57.0 ms, 5.4 ms, and 4.3 ms, respectively. Spectral analysis was used to detect rhythmical oscillations in these time series. The power spectra densities of both heart rate and ventricular repolarization during show peaks in the same frequency bands: low frequency (0.05-0.12 Hz) and high frequency (0.2-0.4 Hz). The power distribution between these two bands observed in the ventricular repolarization duration spectra was found to be the reverse of that in heart rate spectra (p less than 0.005).

Multifunctional Branched Gold−Carbon Nanotube Hybrid for Cell Imaging and Drug Delivery

Branched gold nanoparticles were grown on oxidized multiwalled carbon nanotubes by one-step reduction of gold chloride in water. The carbon nanotube/gold hybrids were used for the delivery of the anticancer drug doxorubicin hydrochloride into A549 lung cancer cell line. Doxorubicin (Dox) can be adsorbed in high quantity on both inner and outer surfaces of oxidized carbon nanotubes by π-π stacking interactions between doxorubicin aromatic groups and carbon nanotube (CNT) backbone. Carbon nanotube/gold hybrids display a broad absorption band in the red and near-infrared regions allowing their use for imaging applications. In vitro cellular tests showed that the nanostructures can efficiently transport and deliver doxorubicin inside the cells.

Structural and compositional study of B–C–N films produced by laser ablation of B4C targets in N2 atmosphere

Abstract In this work, we report on a structural and compositional characterization of B–C–N thin films deposited by laser reactive ablation of a B4C target, in low-pressure (5 Pa) nitrogen atmosphere. For target ablation, a KrF excimer laser (λ=248 nm, τ=20 ns) has been used, at the fluences of 6 and 12 J/cm2. Films have been deposited on silicon 〈100〉 substrates at room temperature. Scanning electron miroscopy (SEM), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and Fourier transform-infrared spectroscopy (FT-IR) characterization techniques were used to analyze the composition and the structure of the deposited films. The film results to be a mixture of sp2/sp3 BN and sp2/sp3 nitrogenated C phases. The concentration of the different BN phases depends on the used laser fluence for the deposition of the film.

Graphene-based technologies for energy applications, challenges and perspectives

Here we report on technology developments implemented into the Graphene Flagship European project for the integration of graphene and graphene-related materials (GRMs) into energy application devices. Many of the technologies investigated so far aim at producing composite materials associating graphene or GRMs with either metal or semiconducting nanocrystals or other carbon nanostructures (e.g., CNT, graphite). These composites can be used favourably as hydrogen storage materials or solar cell absorbers. They can also provide better performing electrodes for fuel cells, batteries, or supercapacitors. For photovoltaic (PV) electrodes, where thin layers and interface engineering are required, surface technologies are preferred. We are using conventional vacuum processes to integrate graphene as well as radically new approaches based on laser irradiation strategies. For each application, the potential of implemented technologies is then presented on the basis of selected experimental and modelling results. It is shown in particular how some of these technologies can maximize the benefit taken from GRM integration. The technical challenges still to be addressed are highlighted and perspectives derived from the running works emphasized.

Autonomic changes during pregnancy: Assessment by spectral heart rate variability analysis

The aim of this study was to investigate cardiovascular autonomic balance in normal pregnancy through spectral analysis of heart rate variability. For this purpose, electrocardiograms were recorded in 8 nonpregnant women and in 32 pregnant women at 10-39 weeks of gestation. Low-/high-frequency peak (LF/HF) ratio was used as an indirect index of sympathovagal balance. In left lateral recumbency, the LF/HF ratio was lower in pregnant women than in control subjects at all gestational ages. The LF/HF ratio was not affected by turning from left lateral to supine recumbency in control subjects, whereas it significantly increased in pregnant women (eg, from a mean +/- SD of 1.05 +/- 0.81 to 2.18 +/- 1.69 after the 33rd week of gestation). Handgrip at low intensity remarkably increased the LF/HF ratio both in control subjects (from 2.21 +/- 2.76 to 2.73 +/- 1.91) and in pregnant women (from 1.28 +/- 1.17 to 2.24 +/- 0.95 at 34-39 weeks of gestation). The results suggest that a rearrangement of autonomic tone takes place in normal pregnancy, which could be interpreted either as a shift of autonomic balance toward a relative vagal predominance or as the consequence of attenuation of baroreflexes.

Development of DLC film technology for electronic application

Abstract The issues related to the development of a carbon film technology for microelectronic applications are considered in this paper. To this end, carbon films deposited by plasma assisted chemical vapour deposition (PACVD) and by magnetron sputtering of a graphite target are analysed comparatively. A great deal of information about them is shown to be gained by combining two analytical methods. On the one hand, in situ X-ray reflectivity (XRR) allows us to monitor, in real time, parameters such as thickness, density and surface roughness of the growing film. On the other hand, ex situ X-ray photoelectron spectroscopy (XPS) provides knowledge about the chemical composition and the electronic structure of the film surface region. Combination of such complementary analytical techniques results in a powerful tool for the development of the required technology to enable the use of diamond-like carbon (DLC) films in microelectronics devices.

Sustained in vitro release and cell uptake of doxorubicin adsorbed onto gold nanoparticles and covered by a polyelectrolyte complex layer

Gold nanoparticles functionalized with doxorubicin and stabilized with multilayers of degradable polyelectrolyte were allowed to age in aqueous medium in vitro in order to show the possibility of drug release in cellular environment. The chemico-physical characteristics of the nanoparticles are reported. The observed release of doxorubicin (DOX) was pH-dependent, and it increased in acidic environment. Cell uptake of nanoparticles and drug release were monitored by laser scanning confocal microscopy. Data showed that drug-bearing nanoparticles delivered DOX into the nuclei of A549 cells, leading to pronounced cytotoxic effects to this lung tumor cells. Our results suggest that gold nanoparticles conjugated with doxorubicin could be used as a pH-triggered drug releasing carrier for tumor drug delivery.

The C1s core line in irradiated graphite

Recently, plasma deposited amorphous carbon films have been the subject of extensive experimental and theoretical investigations aimed at correlating their electronic, structural, and mechanical properties to growth parameters. To investigate these properties, different spectral parameters reflecting the electronic structure of carbon-based materials are proposed in literature. The effects of various electronic configurations on the carbon photoelectron spectra are analyzed here with particular attention to C1s core line with the aim to better interpret its structure. The latter is commonly fitted under the assumption that it can be described by using just two spectral components related to sp2 and sp3 hybrids. Their relative intensities are then used to estimate the sp2 and sp3 phases. We show that, in the presence of an amorphous network, the C1s line shape is the result of a more complex mixture of electronic states. Ar+ irradiated graphite and successive oxidation was used to identify spectral feature...

Nanocomposite Er-Ag silicate glasses

Particular attention has being given to metal–dielectric nanostructured materials, due to the well known surface plasmon resonance, described as the oscillation of the free electrons with respect to the ionic background of the nanoparticle when they are collectively excited by laser irradiation. It is claimed that metal nanoparticles can be used for increasing the intensity of the luminescence emitted by rare earth ions. This effect is attributed to the strong absorption cross section related to the surface plasmon excitation in noble-metal nanoparticles and/or to the large local field enhancement generated around the excited nanoparticles. In spite of the large amount of work published on this topic, the mechanism of optical amplification remains controversial. Here we present x-ray photoelectron spectra and transmission electron images together with photoluminescence absorption and emission measurements, with the aim of providing a better understanding of the effective role of silver as a sensitizer for erbium.

Processing and characterization of diatom nanoparticles and microparticles as potential source of silicon for bone tissue engineering

Silicon plays an important role in bone formation and maintenance, improving osteoblast cell function and inducing mineralization. Often, bone deformation and long bone abnormalities have been associated with silica/silicon deficiency. Diatomite, a natural deposit of diatom skeleton, is a cheap and abundant source of biogenic silica. The aim of the present study is to validate the potential of diatom particles derived from diatom skeletons as silicon-donor materials for bone tissue engineering applications. Raw diatomite (RD) and calcined diatomite (CD) powders were purified by acid treatments, and diatom microparticles (MPs) and nanoparticles (NPs) were produced by fragmentation of purified diatoms under alkaline conditions. The influence of processing on the surface chemical composition of purified diatomites was evaluated by X-ray photoelectron spectroscopy (XPS). Diatoms NPs were also characterized in terms of morphology and size distribution by transmission electron microscopy (TEM) and Dynamic light scattering (DLS), while diatom MPs morphology was analyzed by scanning electron microscopy (SEM). Surface area and microporosity of the diatom particles were evaluated by nitrogen physisorption methods. Release of silicon ions from diatom-derived particles was demonstrated using inductively coupled plasma optical emission spectrometry (ICP/OES); furthermore, silicon release kinetic was found to be influenced by diatomite purification method and particle size. Diatom-derived microparticles (MPs) and nanoparticles (NPs) showed limited or no cytotoxic effect in vitro depending on the administration conditions.